Relay contact and method of making the same



March 10, 19 25 1,529,616

F. L4 DODGSON RELAY CONTACT AND METHOD OF MAKING THE SAME Filed Jan. 13,1919 2 Sheets-Sheet 1 E rs "tum: Q! /7 23 24 A TTORNE I March 10, 1925.1,529,616

F. DODGSON RELAY CONTACT AND METHOD OF MAKING THE SAME Filed Jan. 13,1919 2 Sheets-Sheet 2 INVENTO BY M/ I ATTORNEY Patented Mar. 10, 1925.

UNITED STATES PATENT OFFICE.

FRANK L. DODGSON, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILWAYSIGNAL COMPANY. OF GATES. NEW YORK. A CORPORATION OF NEW YORK.

RELAY CONTACT AND METHOD OF MAKING THE SAME.

Application filed January 13, 1919.

To all whom. it may concern Be it known that l, FRANK L. DonosoN, acitizen of the United States, and resident of the city of Rochester, inthe county of Monroe and State of New York, have invented a new anduseful Relay Contact and Method of Making the Same, of which thefollowing is a specification.

This invention relates to an improved construction of a contact forrelays used in railway signaling systems, and to a method of making suchan improved contact.

It is important to have low resistance between the contacts of relaysused in railway signaling systems, especially contacts in motor circuitswhere the resistance of the contact, if high, constitutes a largeproportion of the total resistance. It has been proposed to obtain suchlow contact resistance by employing metal In metal contacts, but suchcontacts are objectionable because the arcing or sparking, gcncrallyoccurring upon separation of the contacts, causes the contact surfacesto become pitted or roughened, thus increasing the contact resistanceand necessitating frequent renewal. Moreover, the interruption ofcurrent often draws an arc across the relay contacts as they separate,sufficient in some instances to cause the metal to metal contacts toactually fuse together,something which cannot be tolerated in railwaysignaling systems, because safety requires actual separation of contactsat the proper time. The metal to metal con tacts in railway signalingrelays are specially susceptible to such fusing because the forcetending to cause separation of the contacts is small. Lightning andother heavy current discharges accentuate this ditliculty, so that theolriectionable features of metal to metal contacts has led to the use ofcarbon, graphite, or some similar refractory material for one or both ofthe contacts. Graphite to metal contacts, however, have thedisadvantages that the contact resistance is high and often variable.

\l'ith these considerations in mind. it is contemplated. according tothis invention. to provide a relay contact in which the actual makingand breaking of the circuit will occur between metal and graphite. whilethe flow of current: in the circuit will take place through the lowresistance of a metal to Serial No. 270.970.

metal contact. Such a construction gives the desired low resistance forconducting the current, and at the same time provides for thesatisfactory making and breaking of the circuit.

I am aware that it has been heretofore suggested to make and breakcircuits be tween carbon to metal contacts, as in the well known circuitbreaker: but the application of this idea to the delicate relays used inrailway signaling, presents a number of diilicuit problems, which it isthe purpose of my invention to solve. The contacting parts in a relaymust be light, bccause of the small amount of energy avail able foroperating them. For example, in the relay in which 1 am familiar theoperat ing force for each pair of contacts is only about one ounce. Yet,the contacts must have a substantial and rugged construction suflioientto Withstand long service under wide variations of temperature andatmospheric conditions.

Also, the requisite operating characteristics of railway signalingrelays, together with the small size of parts and the small amount ofoperating force available, imposes certain limitations upon theconstrut. tion not found in other circuit controlling devices. In arelay contact, one member should he resilient so as to make a good firmcontact with the other member. and also to cause a scraping or abrasionof the contact surface of said other member as the contact members arehrtmght together. It likewise important to have a spring action at thecontact members of a relay so as to provide an initial pressure, whenthe relay s energized, tending to force the armature away, or in otherwords, assist in the dropaway of the armature. The small amount ofoperating force available, for exam ne. only one ounce per pair ofcontacts), requires that the resiliency or springaction foraccomplishing these two functions should be con'ihined and derived fromthe same member. This is EUPUHII'JllSliKtl in the relays with which I amfamiliar. by making one contact member resilient and shaping it suchthat it rubs across the contact fa e of the other contact member duringthe closing movement, the resiliency of this same mcm her affording thedesired spring action both For kicking ofi' the armature when the relayis deenergized and for making good coir tact. lVhen an attempt is madeto incorporate with such a contact construction the l'unctions of makingand breaking the circuit between graphite and metal, while maintainingthe circuit between metal and metal, it will be evident that a stillfurther spring action is required, for the reason that the initialcontacting between the graphite and metal contacts, upon energization ofthe relay, must give way to permit the contacting of metal to metalcontacts, while on the other hand, upon deenergization of the relay, thecontacting between graphite and metal must follow up and succeed thebreak ing of the contact between metal and metal. ll? it is attempted toobtain this latter spring action from the resilient contact member, itfound that the duty imposed is too great for satisfactory and reliableoperation These limitations impose conditions upon the construction of aContact suitable for re lays used in railway signaling which are notfound in ordinary circuit breakers and simi lar devices.

Also, the requirements or performance of relays, especially in thebreaking of circuits, are also extremely exacting. The parts r;lt0llltlbe constructed so there is no chance of binding or sticking, sincestately requires the separation of contacts at the proper time, eventhough the force tending to produce separation is very small.Furthermore, any construction meeting these requirements should also beone which can be made by ordinar manufacturing methods by averageskilled abor.

One of the principal objects of this invention, is to provide a relaycontact having those essential and desirable characteristics, which issimple, practical, and reliable in its operation, and which willwithstand long service under severe operatin conditions.

After a satisfactory construction of a relay contact has beendetermined, it is found that the making of its delicate parts, and theassembly and fastening together of these parts in the relationrequiret'l, together with proper clearances for satisfactory operation,presents a number of diliicult problems; and a further object of myinvention is to devise a method of making a relay contact oil thecharacter described which can be practiced rtliriently by averageskilled labor, and which can be used commercially to produce a relaycontact hav ng the desired teaturcs oi construction and operation.

Uiher objects and advantages or my in xeution will appear thedrscription prti gresses; and the novel features oi the invention willbe pointed out in the appended claims.

in descriijing the invention in detail. reference will be made to theaccompanying drawing, in which is illustrated a preferred physicalembodiment of the invention, in which like reference characters refer tocorresponding parts in the several views, and in which:

Fig. l is a view in side elevation of a relay of well knownconstruction, showing a contact embodying my invention applied thereto;

Fig. 2 is a view in end elevation of the relay shown in Fig. 1;

Fig. 3 is an enlarged section of a contact cn'ibodying my invention,taken substantially on the line 3--3 in Fig. l and looking in thedirection indicated by the arrow a, the parts of the contact being inthe open position corresponding to the deenergized condition of therelay;

Fig. 4 is a fragmentary section, similar to Fig. 3), showing the partsin the closed position, corresponding to the energized condition oi therelay;

Fig. It illustrates in perspective the separate parts of the contactdisassembled;

Fig. (3 is a perspective vicvv ol' the apparatus used in accordance withmy invention to assemble and fasten together the parts of the relaycontact;

Fig. 7 is an enlarged vertical section through the apparatus shown inFig. (3;

Fig. 8 is an end view of the stopper plunger forming a part of theapparatus shown n Fig. 7; and

Fig. 9 is a perspective view of another part of the apparatusillustrated in Fig. T.

Referring tirst to the general construction of the well known type ofrelay shown in Figs. 1 and 2, this relay comprises the usual pair oicoils L with a back strap :2, and pole pieces 3 fastened to a coilsupport t, all of these parts being supported by the top plate 5 ol therelay casing. This casing consists of the metal top plate a hastplate 6,and glass walls or sides T, \Yllllll are clamped between the top plateand the base plate by screws o. The armature .l of the relay ispivotally supported at one edge to downwardly extending lugs it)integral with the coil support l. A number of contact lingers 11 arefastened to the armature l) with interposed pieces 12 of insulatingmaterial. Each contact linger 11 is provided at one end with resilientcontact pieces 1 and l-t which are adapted to cooperate with lixcd backand trout contacts. respectively. 'lhcse front and back contacts are inthe form of binding i iost's R and F. with which the parts actuallytouching the contact pieces 13 and it are associated. The oppw site endof each contact tinger 11 is clro trically connected by a flexiblecondurtor if to a binding post secured to and ii striated troin the topplate I. have shown my invention applied particularly to theconstruction of the trout contact or binding post F. Referring to Figs.3 and 4, the front contact post F comprises a stem 16, which is screwthreaded for part of its length at one end and which has an enlargedhead or holder 17 at its lower end. The base portion of the holder 17 issquared and fits without turning: in a groove in the bottom of a block18 of insulating material Whichextends across the under side of the topplate 5. The stem 16 extends through a larger hole in the top plate 5and through a bushing it) of insulating material. A sleeve 19 of treatedsilk or similar insulating material surrounds the stem 16 and insulatesit from the metal top plate 5: and the whole front contact post 1 isclamp-ed in place by a nut 21. (Fig. 1). the post being provided withthe usual nuts 22 for attaching wires.

The holder 17 of the contact post F has an axial cylindrical cavityformed therein. the lower end of which is counterbored to receive acontact member or button 2?, of carbon. graphite, or other refractoryllltt' terial. This button 23 is formed with a lower cylindrical portionslightly less in diameter than the counterbore in the holder 17, andwith a smaller guiding collar, and is bored axially to fit freely andsnugly around a contact pin24 of silver or other good contact material.This pin 2i has a thin cylindrical head 25 at the lower end: and in thelower end of the graphite button 23 is a cylindrical recess which isslightly deeper than the thickness of said head of the pin. The upperend of the contact pin 2-4 is fastened to the holder 17. and between thebottom of the cavity in said holder and the button 23 is interposed alightcompression coil spring 26, which tends to urge the but ton 23downward to the position, shown in Fig. 3, where the head 25 of the pin24 limits further movement, and the lower contact surface of the button23 is below the contact surface of the head 25.

I prefer to make the contact finger 11 of brass or similar goodconducting material of the requisite stiffness, the contact piece 1 andpin 24 of coin silver or other highly conductive and non-corrodingmaterial. and the button of graphite or other refractory material havinggood conducting properties.

One of the important features of the invention is the Way of fasteningthe contact pin 24 to the holder 17. The upper end of the pin 24:extends into an axial bore in the holder 17; and the upper end portionof said pin is reduced in diameter. so as to leave a shoulder whichbears against the bottom of the cavity in the holder IT. This upper endportion of said pin 24 is formed with gripping edges or shoulders.preferabl 7 formed by a circumferential groove 27; an when the pin 24 isin place this groove 27 is aligned with a transverse hole 28 in theholder 17. After the parts are properly positioned. as hereinafterexplained, solder 29 is run in the hole around the upper end of the pin24. thereby securely fastening the pin in place.

lVith the relay deencrgized,the parts of the contact device assume thenositions shown in Fig. 3, the sprinf 26 having moved the graphitebutton 23, guided by the pin it, to its lowermost position, where thelower face of the head 25 of said pin is above the lower face of thebutton 2;}. lVhen the relay is energized, and its armature fl isattracted, the front contact piece 1;} of the contact linger 11 moveupward y and makes contact first with the graphite button 23. Thepressure of the spring 2:; on the button 23, however. is made slight andless than the pressure whi h the contact linger exerts, so that thebutton is moved upward until the pressure of the contact finger fallsdirectly upon the enlarged head :25 of the contact pin :24. thusestablishing a direct metal to metal connection from the contact finger11 to the binding post F. This position of the parts is shown in Fig. 4.

Vhen the relay is again deenergljizcd. its armature and its contactfingers are c turned to their lower position by their weight. During;this movement. the but 33, being! urged downward by the sprin willfollow up the downward movement of the contact piece 3. C(uiscuucutiy.the con tact piece 13 first leaves contact with the head of the pin 24-.thereby separating the metal to metal contacts but leaving: the cir cuitcompleted through the graphite button '23; and then, when the downward'l ollovvaip movement of the button 23 is arr s d by the head 25 of thepin 24 (sec Fl: :1). the contact piece 13 finally breal-cs contact thebutton 23. thereby illicl'l'lll iiilig the cur rent between graphite andmetal. Thus. it will be, evident that my invention provides aconstruction in which the initial hm JiEw final breaking of the circuittakes p tween a refractory material and a while the circuit isestablished \hio low resistance of a metal to metal to it will beobserved that the con iruction described is simple and compact. 'liiegraphite button .2 3 and the contact pin it are combined into a unitary41 ructurc adaptcd to cooperate with a single metal contact piece. Thespring: action. demanded to bring about the breaking" and lllilix'lllgjoi the i'li' cuit between graphite and metal. i derived from the sprin;"26. indepeiulently of the resiliency of the contact piece i i. therebydividing the duties imposed upon the parts and satisfying: thelimitations of ii llll lion previously explained. The from contact postl embodying the invention. can be readily applied to any of the pre enttypes of relays. and if desired. may be an and metal.

act

aligned, the plunger 30 is again projected to hold the assembled partsof the contact post firmly in the proper position.

It will be noted from Fig, 7 that the spacing member S bears against thepin 24, the

shoulder of which in turn bears against the bottom of the recess in theholder 17. This positions the pin 2i lengthwise of the con tact post Fin the relation desired to adapt it for incorporation in a i nnpleterelay. The pin 2i is positioned AIL-1137' in the exact relation desiredby reason of being guided by the button 23, which in turn is positionedaccurately with regard to the holder 17 by the thin collar 44; on thespacing member S. It will be evident that the primary factor determining the precise axial alignment of the pin desired, provided theparts are other wise within the narrow limits readily attaincd inordinary manufacturing, is the clearance between the graphite button 23and the holder 17, such as to permit the but ton to slide easily withoutany chance of binding. This desired relation is what is obtained by thespacing member After the parts are in position, a short cylindricalpiece of solder all is inserted in the upper end of the hole in theholder 17, this piece of solder being long enough to stick out slightlywhen resting on the pin The holder 17 now heated, preferably by theflame of a torch or similar heating appliance, the flame being appliedas indicated at 47 in Fig. 7. The operator watches the projecting upperend of the piece of solder 4-6 carefully, and as soon as this piece ofsolder melts and disappears, an additional piece of solder 4:8 is alsodropped in, and the flame withdrawn. The parts are then allowed to cool,or are cooled artificially by a blast of air. if desired, and thecontact post removed and inspected. If solder can be seen from the lowerend of the hole 28, it is known that a proper joint has been made. Thefact that solder has run past the 'pin 24-, proves that this solder musthave formed around the groove 27 in the end portion of this pin. andalso that the solder must have been hot enough to make a good joint.

The purpose of putting in the piece of solder ltiinto the holder 17before heating it, is to provide a simple and reliable way ofdetermining when the holder 17 has been heated sufliciently to properlymelt the solder. Obviously, overheating should be avoided, because it isliable to distort the parts and injure the spring 26. The stopperplunger 38 prevents the solder from running out of the hole 28, andsince this plunger is made of aluminum, the solder will not stick to it.The cross cuts 39 in the upper end face of the stopper plunger 38 affordvents to allow the heated air or gases to pass out from the hole 28without interfering with the desired movement of the solder. Theapparatus illustrated provides for the assembling of one contact post,but obviously several similar base blocks may be used in gangs, ifdesired.

This application is a continuation in part of my prior application,Serial No. 226,708, liled April a 1918.

Although I have particularly described the construction of one physicalembodiment. of my invention, and explained the operation and. principlethereof; nevertheless, I desire to have it understood that the formselected is merely illustrative, but does not exhaust the possiblephysical embodiments of the idea of means underlying my in vention.

l'Vhat I claim as new and desire to secure by Letters Patent of theUnited States, is:

l in a relay for railway signaling, a contact construction comprising,an insulated contact post having a cup-shaped end, a metallic pin fixedto said post within its cupshzmed end and extending axially thereof,said pin having an enlarged head at its outer end, a carbon buttonpartially enclosed within the cup-shaped end of said post and sunrounded and guided by said pin, said button having a recess in its outerend to receive the enlarged head of said pin, this recess be ing deeperthan the thickness of said head a compression coil spring within thecupshaped end of said post and acting to press said carbon buttonoutward to a definite position determined by the engagement of the headof said pin with the bottom of the recess in the button, and a movablecontact fin ger having a flat resilient contact piece at its endengaging the button before and after engagement with the pin duringmovement of the finger toward and away from the post respectively,whereby electrical contact between the finger and post is broken betweencarbon and metal and is maintained between metal contacts.

2. In a relay of the type described, a contact arrangement comprising,an insulated contact post having a cylindrical recess in its outer end,a pin of highly conductive material fixed to said post and extendingaxially thereof within said recess, a carbon button. of generalcylindrical shape having an axial bore to receive said pin, a springwithin said recess acting to press said button outward, means limitingthe outer position of said button to a point where its contacting faceis beyond that of said pin, a contact finger having a resilient flatcontact piece at its free end disposed at an acute angle to the axis ofsaid button and pin, said finger being movable with respect to the postto cause electrical contact between said button and contact piece of thefinger before and after contact between the pin and the contact piece asthe finger is moved toward and away from the post, respectively, theangulit) lar disposition of the contact piece causing it to slide overthe contacting surfaces or said button andpin, whereby a rubbingengagement of metal-tonietal contacts is employed for i'naintainingcircuit connections while the circuit is broken by the rubbingengagen'ient of metal to-carbon contacts.

In a contact construction for relays of the type shown and described, astationary contact post having a recess, a :arbon button within saidrecess formed with a circumferential shoulder to engage the post aroundsaid recess, a metallic pin tired to said post and passing through anaxial hole in said button, said pin having an enlarged head at its outerend, the button having a recess in its outer face to receive the head ofsaid pin, the cooperation of the button with the head of the pinlimiting the outer movement of the button, means urging said buttonoutward and a movable contact member engaging both the button and pinand exerting a pressure sufiicient to force the button inward and permitthe meaning of a direct metal-to-nietal contact between said member andthe enlarged head of said pin.

4. A relay for railway signaling having, in combination, a movablecontact finger carried by the armature of the relay, a fixed metallicpin, and a movable graphite button surrounding said pin and springpressed toward said contact linger. said pin and but ton being botharranged to cooperate with said linger, said parts co-acting to make andbreak the circuit between the contact finger and the graphite button andto maintain the circuit through the contact linger and the metallic pin.

A relay for railway signaling having, in combination, a movable contactfinger carried by the armature of the relay, and a contact post forcooperating with said contact finger, said post comprising a stem havingan axial recess therein, a movable member of conducting refractorymaterial in said recess, and a metallic member of highly conductorymaterial attached to said stem, said movable member being yieldinglybiased into position to make contact first and last with said contactfinger as the latter is moved toward and from the contact post, wherebythe circuit is made and broken between a metal and a refractory materialand is maintained between metal and metal.

6. In a relay, the combination with a mom able contact finger, a contactpost tor cooperating with said finger and provided with an axial recess,a carbon button in said recess movable lengthwise of the post, a springenclosed in the recess and pressing the button outward, and a fixedmetallic contact member of highly conductive material coacting with saidbutton to limit the outward movement thereof to a position in which thecontact face of the button is nearor the contact finger than that of themetallic contact, whereby the contact finger engages the button and themetallic contact in succession as it. moved to its attracted position.

7. A graphite-metal contact for relays comprising a fixed metallic pin,a movable graphite button surrounding said pin, and resilient means torurging said button to a position where its contacting face is beyond thecontacting face of said pin.

8. A graphiteanetal contact for relays comprising a circular pin ofhighly conductive material, a movable graphite bub ton surrounding saidpin and guided thereby, said pin and button coacting to limit themovement of the button to a position where the contact face thereof isbeyond that of the pin, and a compression coil spring acting to urgesaid button to its projecting position.

9. A graphiteanetal contact for relays con'iprising a silver pin formedwith an enlarged head, a graphite button surrounding said pin andmovably guided thereby, said button having a recess in one end faceadapt-- ed to receive the head of said pin, and a spring yieldinglyholding said button prw jected against the head of said pin, the contacting end face of said button when projected being beyond the contactsurface of the head ol said pin.

10. A cont-act post for relays comprising a stem and an enlarged headhaving an axial recess therein, a metallic pin attached at oniend tosaid head and extending out of the recess lengthwise of the post, agraphite button surrounding the pin and partially enclosed in saidrecess. and a. compression coil spring in said recess tending to movethe button outward, said button being limited in its outward movement toa position where its contacting face is beyond the outer end face of thepin.

11. A contact construction for relays cone prising a post, a metallicpin extending axially of the post and fastened thereto at one end, agraphite button guided by said pin, said pin being adapted to cooperatewith said button and limit the movement thereof to a position where itscontacting face is beyond that of the pin, and a spring acting to movethe button outward.

12. A contact construction tor relays comprising a contact post, ametallic pin haring one end portion thereof roughened and extending intoa bore in said post, said post having a hole therein intersecting saidaxial bore and filled with solder which embraces the roughened endportion of the pin and holds it in place, a movable graphite buttonsurrounding the pin, and means for resiliently urging said button to aposition where its contacting face is beyond that of the pin. 13. Acontact construction for relays in which a metallic contact pin isfastened at ill) tit)

one end to a contact post by solder in a hole in the post extendingtransversely of the axis of the pin and which embraces gripping edgesformed on the end portion of said pin.

14. In a relay, the combination with a vertica ly movable contactfinger, a contact post for cooperating with said finger and providedwith an enlarged head having an axial recess therein. a button ofconducting refractouv material in said recess and yield ingly projectedoutward to a limited extent lengthwise of the post, and a fixed metallicmember of highly conductive material havinc its contact face within thelimits of the outer contacting face of said button. said contact face ofsaid metallic member being in a horizontal plane above that of the but'ton while the button is in its projected po sition.

15. In a relay. the combination with a movable contact linger having aresilient contact piece at one end. a contact post comprising a stemadapted to be fastened to the top plate of the relay, a fixed metallicpin of relatively low resistance attached to said stem and provided witha contact face at its lower end. a spring. and a movable *arbon buttonsupported by said pin and normal y positioned by said spring so as to beengaged first by said contact piece as the finger is attracted. saidcontact piece on the finger being: inclined with respect to the faces ofsaid stem and button so as to rub over them as the finger is attracted16. A contact post for relays comprisin; a stem adapted to be attachedto the top plate of the relay. a metallic contact member attached tosaid stem. a carbon lmtton movable lengthwise of the stem and having itsoutward movement limited by said metallic member so as to have itscontact face beyond that of the metallic member. and a spring acting topress said button outward.

1T. contact post for relays comprising: a stem adapted to be attached tothe top plate of the relay and provided at one end with an enlarged headhaving a recess therein. a carbon button in said recess in vablelengthwise of the stem. a metallic contact member secured to said stemand adapted to limit the outward movement of the carbon button andposition it with its contact face beyond that of the metallic member.and a sprin; enclosed in said recess for press in; said button outward.

19. A contact post for relays comprising a stem adapted to be attachedto the top plate of the relay. a carbon button carried by said stem andmovable lengthwise thereof. a metallic contact member fastened to saidstem and having a contacting part within the limits of the outer contactface of said button. said button having a recess in its contact face toreceive said contacting part of the metallic member. and a spring forpressing said button outward.

19. A contact post for relays comprising a stem having an axial recesstherein. a

'arbou button in said recess. and movable lengthwi e of the stem. saidbutton having an axial bore lcng'thwiic thereof. a spring enclosed inthe recess and acting to press said button outward. a metallic member ohighly conductive material attached to said stem. said metallic memberpassing through the bore in said button whereby said button and metallicmember are disposed with their contact faces one within the limit of theother. and means whereby the outv; rd movement of the button is limitedso as t position its contact face normally outside f that of themetallic member.

2t). A contact post for relays comprising a stem having an enlarged headwith a downwardly opening axial recess therein. a carbon button in saidrecess and biased to move downward lengthwise of the stem to aprwtetcrminc l project ed position. and a metallic member of highlyconductive ma terial attached to said head with its contact face withinthe limits of and above the con tact face of the button in it lmverproje ted position.

.21. contact post for rciays. comprising a stem screw threaded f r partof its length at one end and having an enlarged head at its other end:said enlarged head havin j a cylindrical cavity formed therein which i:'counter-bored at one end: a condu tive bu ton of refractory materialadapted to l'ai t I lit in the couuterlmre f said cavity. said buttonhaving" a hole pa sing therethrmua'h which is counterbortal at one end:a metal lic pindle of relatively low resistance ex tending through saidreces and rigidly ecured to said stem. said spindle having;- a shankadapted to pass through the hole in said button and also having anenlarged head at one end adapted to fit loosely in the counterborc insaid button and to loosely hold said button in position. the thicknessof the head of said spindle being less than the depth of the countcrborein said button: and a spring. housed in said cavity and adapted tospring); press said button ontward in one direction. the movement ofsaid button being limited by the under side of the head of said spindle.

22.11) a relay. the combination with a movable contact linger having aresilient contact piece at its outer end. of a statioiu ary contact postcooperating! therewith and comprising a fixed metallic member of highlyconductive material. a movable member of conducting refractory material.and a spring. said movable member being normal- 1y projected by thespring into position where its face nearer said contact piece than themetallic member. the tension of llt) said spring being less than that ofthe contact piece, whereby the contact piece makes contact successivelywith the refractory member and the metallic member.

23. The method of making graphite-metal contacts for relays of the typeshown and described in which a small contact pin is fastened at one endto a contact post and a graphite button is guided by said pin andpartially embraced by parts of the post, said method consisting inpositioning the pin in proper relation to the contact post by holdingthe button in alignment with the adjacent parts of the post embracing itwith an intervening space for clearance, and then fastening the pin tothe post in the position thus established.

24. The method of making graphiteanetal contacts tor relays of the typeshown and described. in wihch a small pin with a roughened end portiontits loosely in a bore in a post intersected by a transverse hole insaid post, said method consisting in assembling and holding the pin inthe proper relation to the post. heating the post, and then runningsolder into the transverse hole around the roughened end portion of saidpin.

25. The method of making grzqtihite-metal contacts for relays of thetype shown and described. in which a small pin with a roughened endportion tits loosely in a bore in a post intersected by a transversehole in said post, said method consisting in assem bling and holding thepin in proper relation to the post, inserting a piece of solder into oneend of the transverse hole with part of the solder sticking out insight, and then heating the post until the solder melts and disappears.

26. The method of making grapl1itemctal contacts for relays of the typeshown and described, in which a small pin with a roughened end portiontits loosely in a bore in the post intersected by a transverse hole insaid post, said method consisting in assembling and holding the pin inproper relation to the post, covering one end of the transverse hole inthe post with a vented stopper, and then running solder into the otherend of said transverse hole around the roughened end portion of saidpin.

27. A contact construction for relays colnprising, a stationary metalliccontact. a movable contact member ot refractory lnateriat having arecess therein to receive the coin tacting portion of said metallicmember, and a movable finger for engaging said metallic contact and saidrefractory member, the contact between said finger and metallic memberbeing broken in a substantially closed chamber formed by the recess insaid member of refractory material.

28. Contact construction for relays, comprising a stationary metalliccontact, a movable finger arranged to engage said contact. and a movableconducting refractory mene ber partially enclosing said stationarycontact and co-operating with the finger to form a closed chamber aroundthe contacting portions of said finger and stationary contact whencontact between the latter is broken.

FRANK L. DODGSON.

